Method and apparatus for molding hollow pulp articles



Feb. 16,

METHOD AND APPARATUS FOR MOLDING HOLLOW PULP ARTICLES Filed May 12, 930

30! luye tz a difiiculty, it has been proposed to pass a gas- Patented Feb. 16, 1932 UNITEVDI S ATES PATENT OFFICE EUGEN xATz, or BERLIN-CHARLOTTENBURG, GERMANY, Assrenon To name CON- TAINER CORPORATION, or BOs ON, MASSACHUSETTS, A CORPORATION or MAINE METHOD AND.AJPPABATUS FOR MOLDING HOLLOW PULP ARTICLES Application filed Kay 12, 1930, Serial No. 451,750, and in Germany July 7, 1929.

Methods are known for manufacturing articles from fibrous pulp, in which the amount of fibrous pulp necessary in each case is inmethod, but it has not hitherto been possible to use the method for producing economically large, durable hollow objects, e. g. barrels. The reasonsfor this are as follows.

In the manufactureof solid walls capable of withstanding damage, it; is necessary, as

is recognized in the allied art of paper making, to use a comparatively greasy fibrous pulp. This, however, has the property of being dehydrated only with difliculty. It therefore requires a' high pressure, if the shaping and dehydrating of the hollow 'articles are to be carried out in economically satisfactory time.

If it was desired to use compressed air at such high pressures, the method would be much too expensive. Compressed air requires for its production considerable outlay on motors and compressors.

The small hollow articles to befound on the market are molded from easily dehydrated fibrous pulp. In this case compressed air has been found to be a suitable gaseous pressure medium. But if steam is used, which is obtainable directly from coal and is therefore much cheaper, the drawback is experienced that the steam led into the mold condenses, especially in the earlypart Of the dehydrating period, and that the condensate formed, which is denser than the steam me- 40 dium, escapes ver slowly through the walls of'the article to e made. It thus remains in the mold a long time, and thereby hinders the required firm felting of the fibre.

In order, at least partly to overcome this eous. pressure medium along the interior of the permeable mold and to allow a vacuum to act on the mold from outside, more particularlyin order to assist uniform dehydra-- complicates the apparatus necessary for utilizing such a method that an economical working of the mold with a gaseous pressure medium and a vacuum seems scarcely possible. Moreover, thecondensate is withdrawn too late, namely after it has already passed through thewalls of the mold, and caused damage during the molding.

' This invention overcomes in a simple manner the difficulties hereinbefore referred to. First, the superheated gaseous pressure medium is given the opportunity of partly es-' c'aping from theinterior of the mold through a particular adjustable opening after the' pressure medium has given up-its heat or the greater part thereof." Thus the supply of new heat to the interior of the mold is not dependent on the fact, that the pressuremedium has already permeated the walls of the body which is being manufactured.

I In the accompanying drawings two forms of apparatus for carrying the invention into effect are illustrated by way of example and -diagrammatically, in elevation and cross Section, respectively. In Figure 1, a is the hinged mold for an oval hollow object I). The fibrous pulp and the heated pressure medium enter this mold, for example, by the tube a. While a part of the pressure medium escapes through the walls of a and 5, another part can flow out through the adjustable opening val Without having to permeate the walls of the hollow object. By this means, the amount of heat passing in through a per unit of time may be increased at will and the manufacturing process speeded up and thereby made cheaper.

In Figure 2, a is again the mold, b the hollow article to be made, and c the inlet of the heated pressure medium. The direct exit of a part of this pressure medium takes place through the outlet passage 03, which in the present case is made funnel shaped, and begins so near the bottom that it takes up mainly that part of the pressure medium which has already touched the walls of the object to be molded and-has there given up the greater part ofits heat. In order to render this operation more positive and thereby also incorporate the advantages already described in Canadian Patent N 0. 237 ,7 92, the outlet passage d in the present example is led through a body 6 which diminishes the cubical content of the mold. Aspecial advantage of the invention is that it makes possible the manufacture of hollow articles with steam as the only pressure medium, since by meansof the adjustable opening 03 it is possible to remove the condensate formed in the mold in the simplest manner. To this end, the opening d need only open into that part of the'mold where the condensate falls, that is to say, in the case of Figure 1 or 2, directly at the bottom of the. mold a. I

7 That part of the heated pressure medium which escapes from the mold by the opening d, still retains a certain amount of heat. According to the invention this can be recovered by using it for heating the pulp. Thus the tube d may usefully be led into the container which holds the pulp' to be molded.

According to the invention, the introduction of additional quantities, e. g. of steam is no longer dependent on thepermeability of the walls of the molded articles. possible to produce durable articles from greasy fibrous pulp, the fineness of which according-to the scale of Scho'pper-Riegler, exceeds the figure 45. Through the improved process'it is possible to reduce very considerably the permeability to air. Further it is possible to add certain materials a articles from pulp which comprises supplyto the pulp, e. g. colloidal substances, which render the objects molded especially impermeable, more particularly to air.

Among durable articles as described above, large containers come first of all into consideration, e. g. in the form of'casks, boxes, canisters, etc. Such large containers may also be impregnated in any known manner by a later operation, under simultaneous or subsequent mechanical pressing. On account of thelr having no seams, suchlarge containers are partlcularly suited for the despatch of articles of food and table luxuries, chemicals,

salts, etc., and also for the'despatch of goods be produced. Further, the particular advan- It is thus 7 that an unlimited range of shapes is available.

Having now particularly described and ascertained the nature of the said invention and in what manner the same is to be performed, I declare that what I claim is:

1. The method of manufacturing hollow articles from pulp which comprises supplyinga quantity of pulp to a mold, supplying a heated condensable gaseous medium under 7 pressure to the mold to press the pulp against the mold and to efiect dehydration of the molded pulp, allowing part of the medium to escape through the walls of the article being molded to facilitate dehydration of the pulp, and allowing another part of the medium to escape directly from the interior of the molded article, as distinguished from escaping through the walls thereof, after the medium has given up part of its heat.

2. The method of manufacturing hollow articles from pulp which comprises supplying' a quantity of pulp to a mold, supplying a heated condensable gaseous mediumunder pressure to the mold to press the pulp against the mold and to effect dehydration of the molded pulp, allowing part of the medium to escape through the walls of the article being molded to facilitate dehydration of the pulp, and allowing another part of the medium to escape directly from the interior of the molded article, as distinguished from escaping through the walls thereof, after the medium has given up part of its heat, and prior to such condensation of the medium as would maintain or produce a soft or soggy condition of the inner surface of the article.

'3. The method of manufacturing hollow I escape through the walls of the article being molded to facilitate dehydration of the pulp, and allowing the remaining part of the medium and its condensate to escape directly fromthe interior of the molded article, as

distinguished ,from' escaping through the walls thereof, after the medium has given up the greater part of its heat.

4. The method of manufacturing hollow I articles from pulp which comprises supplying a quantity of pulp to a mold, supplyinga heated condensable gaseous medium under pressure to the mold to press the pulp against the mold and to efiect dehydration of the molded pulp, allowing part of the medium to escape through the walls of the article being molded to facilitate dehydration of the pulp, and allowing the remaining part of the medium and its condensate to escape directly from the interior of the molded article, as distinguished from escapinithrough 

